The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs.
For example, focused ion beam or focused electron beam induced deposition has been used for thin film deposition. In such a method, a precursor gas is introduced near a substrate held in a sealed chamber and a focused ion or electron beam causes the precursor gas to undergo molecular dissociation. Dissociated molecules adsorb onto the surface of the substrate, forming a thin film thereon. Film impurity and low deposition throughput have been two main disadvantages associated with these techniques. When focused ion or electron beam is used for forming multiple thin films, further issues arise whereby a thin film formed from one precursor gas is contaminated by another precursor gas used for forming another thin film. Such contamination results in degradation of finally deposited thin films, and therefore should be avoided.